This invention relates to a battery charger and more particularly to apparatus for charging and desulfating a lead-acid type storage battery.
It is possible to reverse the build-up of sulfur crystals on the collectors (plates) of a lead-acid type storage battery. By "hitting" these plates with electrical pulses which produce energy at 3.26 MHz., which is the resonant frequency of a sulfur crystal, the bond is broken, allowing the molecules to dissolve back into the electrolyte solution from which they first came. The only known commercial use of this concept is in products that use a transformer oscillator circuit to generate the required pulse, typically 100 ma. with a 300 nsec. rise time. These devices are not capable of actually charging the battery in the required manner to ensure a fully charged battery, without ever overcharging said battery. Thus they do not require voltage limiting.
Unlike existing devices, this invention is a true two-stage battery charger, capable of fully charging the battery (13.8 V max.) as well as maintaining the battery at a fully charged level (13.2 volts) for indefinite periods, without ever overcharging it. This invention is capable of reversing the build-up of crystallized sulfur on the "plates" of a lead-acid storage battery, thereby improving the charge/discharge characteristics of a battery in which such formations have occurred. It accomplishes this process by rapidly turning the charger on and off (rise time=200-500 nsec.) and by generating pulses (1 Amp amplitude) during the "float" charge cycle.
Because no transformer is used to generate this waveform or to couple it to the battery, this invention is able to produce a pulse which has ten times the energy of a non-charger type device, such as those described in U.S. Pat. Nos. 4,871,959, 5,084,664, 5,276,393 and 5,491,399. The invention simultaneously controls the voltage to 13.2 volts maximum, which ensures that the battery is never over-charged. Non-charging type devices, such as described in the aforementioned patents, do not need voltage limiting, as the pulses they generate are typically only 1/10 (100 ma.) in amplitude of even a low output (1 Amp) charger.
There are other patented techniques to reduce sulfation of lead-acid battery plates which employ pulse techniques. A fast rise time pulse is developed and pulses the battery. See U.S. Pat. Nos. 4,871,959, 5,084,664, 5,276,393 and 5,491,399. All of the techniques rely on a fast pulse developed by a transformer oscillator circuit and specifically include all types of transformer oscillators. These units are not battery chargers. They develop a pulse of about 100 ma. with a 300 nsec. rise time, which has energy at 3.26 MHz. which is the resonant frequency of sulfur crystals. See FIG. 1. When the crystals are subjected to this energy the crystal structure is changed and the molecules dissolve back into the solution and create an active electrolyte.
This invention is different in that it is a battery charger. The charger is connected to a battery and begins the charge cycle. The battery reaches 13.8 volts and then enters a float mode of operation. This mode will prevent the battery voltage from going below 13 volts. In a heavily sulfated battery the voltage will drop below 13 volts and the charger will turn on to try to charge the battery. The charger of this invention is rapidly turned on and off. The charger turn on rise time is about 300 nsec. but the current is 1000 ma., which is ten times higher than the pulse units of the prior art. See FIG. 2. No transformer is used by this invention to generate this waveform or to couple it into the battery. Therefore, this invention generates ten times as much energy with a controlled 13 volt maximum. As the sulfation decreases, less energy is required, and the current decreases to zero at 13 volts. This means that the voltage cannot rise above 13 volts and the electrolyte will not boil away. The prior art pulse units cannot charge the battery so they do not need voltage limiting.
A schematic illustration for the invention is shown in FIGS. 3A and 3B and a parts list table is set forth infra.
An object of the present invention is to provide apparatus for charging and desulfating lead-acid type storage batteries.
Another object is to provide such apparatus which eliminates the requirement for use of transformer oscillator circuits for generating desulfation pulses.
A further object of the invention is the provision of such apparatus which eliminates the need for microprocessors for controlling pulse amplitudes to the battery as the battery is desulfated.
Still another object is to provide such apparatus which rapidly turns the battery charging current on and off to produce desulfation.
Yet another object of the present invention is the provision of such apparatus wherein the rise time of the pulsed charging current is sufficient for effectively desulfating the battery.
Another object is to provide such apparatus which effectively desulfates lead-acid type storage batteries by providing high energy pulses to the battery to both charge and desulfate the battery.
A further object is to provide such apparatus wherein the battery voltage cannot rise above a predetermined level so that battery electrolyte will not boil away.
Another object of the invention is the provision of such apparatus which maintains the battery at a predetermined voltage.
Still another object is to provide such apparatus which does not add an auxiliary pulse on top of a DC charge current to desulfate the battery.
Yet another object of the present invention is the provision of such apparatus which does not require the use of high power pulse generators and complex electronic control circuits to generate high amplitude pulses.
A still further object is to provide such apparatus which is reliable and less expensive than previously known desulfation systems which generate high amplitude pulses on top of a DC charging current.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages are realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.